If you need to be able to do this then you probably have access to an 8i database – which means you create create a table with an index and find out if it is possible almost as quickly as posting a question here.

The request about issues to consider is more appropriate – but apart from the standard comments I make about all index rebuilds, the fact that I can’t think of any special case for 8i at the moment doesn’t mean there aren’t any. In your position, I would have gone to MOS (metalink) and downloaded the patch set note for 9i to check for any patches relating to online index rebuilds. Patches in newer versions tell you about problems in older versions.